Resizing images in photoshop for printing.

[Eleanor5E82]

Hi everyone, I need urgent help with resizing my images for printing.

a. How do I resize my image for printing as is the entire composition in for a particular size with borders (as I am aware that not all images can fit as they were shot)?

b. After its resized what settings do I set it at for the best quality printing if the pixel value is 72, is it okay to set it at 300 DPI, and set the quality to automatic?

Thank you in advance. 

[TheDigitalDog]

What's the SIZE of the output you desire AT a DPI value for the print? You want a 8x10@300DPI, you need 2400x3000 pixels and that's what you'll ask for in the Image Size dialog for interpolation from the original image. Then if you want a border, just use Canvas Size and add that next. 

PPI has absolutely no role in quality per se. It is simply a resolution tag. The tag could be 72PPI or 180PPI but it doesn't have an inherent meaning, only what you could produce with the number of pixels you have at your disposal. Work with pixels! For example, let us say you have 1000x1000 pixels to keep the math simple. And to simplify this further, let's only consider the horizontal axis. If you have 1000 pixels and divide that by 72, that is, you provide 72 pixels per inch, you could end up with 13.8 inches using that division (1000/72=13.8). Let's now say you divide up your 1000 pixels using 180 instead. 1000/180=5.5. In both cases, you had 1000 total pixels. The document itself doesn't have a size, other than what space it takes up on your hard drive. The sizes above are examples of what could be produced if you divided up the total number of pixels you have, with some number of which is just a tag within the document. In Photoshop, if you use the Image Size dialog, turn resample OFF (do not allow it to create more or remove pixels), you can enter any value, 72, 180, 1000 into the resolution field and the resulting size is calculated for you. But you haven’t changed the document or the data at all. You just changed a theoretical 'size' if you output your 1000 pixels using that resolution. So again, it's meaningless until you output the data. At that point, lets say you print the image, you can decide how big you wish it to appear and/or how many pixels you want to devote to the output. You have 1000 pixels and someone tells you that you must use 300DPI (which isn't true but that's a different story). 1000/300 would produce a 3.3 inch print. You want a bigger print? Lower the DPI (within reason). You set the DPI for output to use 180 of your pixels to produce 180DPI? You get a 5.5 inch print (1000/180=5.5).

[Eleanor5E82]

Hi thank you for explaining the technical aspects behind it all and for simplifying the maths behind the pixels and the DPI, this makes life easier now. So what i understand from your explaination is changing the resolution in image size doesn't matter, it could be 72 or 180 or 300, what matters is pixels available? It was confusing because my printer's website asks me to mention what DPI i wish to print my photo at and I was suggested by them to mention 300 DPI there as its the best quality at which a photo should/can be printed?!

Second part of my question was that I am in process of setting up my online stores for selling my landscape and fine art photography both in (landscape and portrait formats), now there are different sizes and the most common ones being 12x16, 16x24, 30x40 etc I am using sony mirrorless camera and the compositions I have I want them to be printed as is without cropping, So i wanted to know how do i fit the photo for any given size with the original composition.

Thank you for your patience and explaning it to me so well, I am grateful.

[TheDigitalDog]

In the Photoshop Image Size dialog, there is a resample check box which allows PS to add or subtract pixels. I'm not sure if that's necessary since I don't know the current resolution (pixels Width and Height) of your document OR the size you want for output. You may have enough pixels where you can simply turn off the resample check box and alter the W&H to a PPI that is sufficient for output. 

This is REALLY an old article but nothing has changed and may help:

http://digitaldog.net/files/Resolution.pdf

[Eleanor5E82]

Hi thank you for the article I read it and I am sorry it didn't say anything about fitting the actual image for a particular size, I am sure I havent put the question in the most eloquent way, Please excuse me. I am simply trying to print my photos with the original composition without having to crop them for a particular size.

For eg: Say I want to print a photo of size 12x16'' but the original photo is not of the size I want to print, then do I have to creat a new document in PS of size say 13x18 and then place my picture in it so it fits the size of 12x16 with borders, with Ctrl+T on mac and then go about it?

Thank you for your help!

[D Fosse]

I don't know what Sony you have, but basically, a good quality file from a current, "upper-midrange-and-up" camera should work for anything - book/magazine spread, poster, roadside billboard, anything. Just leave it as is, don't upsample. It is almost never necessary, and it can only degrade the final result.

For printing, just set the print size as required. As print size goes up, ppi goes down. But here's the thing: the bigger it is, the further away it will be seen from. The eye wants to take it all in, it's almost impossible to resist stepping back from a big print. So the optical resolution on your retina stays the same whatever the physical print size.

Now if you're really critical, inkjet printers have ideal resolutions for the given size. Epsons, for instance, produce a marginally better result when printing a file at 360 ppi. But it's marginal. If you're selling files, just give them the original size that the sensor delivers, and let the customer work it out.

This is from my a7rIII, just to give you an idea. The second is a small crop from the first (at 7952 x 5304 pixels). It should be fairly obvious that there is really no need to upsample these files for any purpose except very special ones:

[D Fosse]

I should add that if you're printing yourself, you'll want to sharpen at final output size. In that case you should resample a copy to that size, at your desired ppi setting (let's just say 360 ppi for Epson, 180 for bigger prints), and then do a careful round of sharpening.

If you're selling files, just send them as they are, maybe with "generic" sharpening just to tighten edges. Not too much.

[NB, colourmanagement net]

Eleanor,]

you write:

"I want them to be printed as is without cropping, So i wanted to know how do i fit the photo for any given size with the original composition."

Of course you will need to set resolution correctly - you mentioned that your print service asks for 300ppi, so ideally you'll give them that.

I think that part of the process has been described well here already.

BUT your question makes me wonder if you're thinking about image propoertion.

IF the desired print format differs in proportions to your original, then to keep the proportions of your original you'll need to either crop to the right proportion [losing some of the original image] or to print with an uneven white border - just set one image edge to fit and allow the other to be set automatically by the "restrain proportions" feature of  image size [the 2 dimensions are linked and a symbol present to show that].

No need to make white borders in a Photoshop image by adding to the "canvas"- the correctly sized image can be placed within the white paper by the printer, leaving a border.

I hope this helps

thanks
neil barstow, colourmanagement.net :: adobe forum volunteer
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[Eleanor5E82]

Hi @D_Fosse & @NB__colourmanagement, Thank you so much for taking time to reply to my questions and answering them so patienly and in details, I appericiate it. 

I use a Sony A7iii for shooting my pictures and yes as suggested by both of you I have made sure to pump the DPI to 300 before sending it across to the printer. My main concern was how do I fit my photos with my original composition without loosing the details in the photo to cropping to fit a particular size.

@NB__colourmanagement What I am generally doing is opening a "new canvas" with size slightly bigger than the size I want to print, say for eg if I want to print a photo to size 12x16", I open a new canvas with slightly bigger size of 13x18" and then place my photo on that canvas and re-adjusting it with ctrl+T and then go to "Image" >> "Image Size" >>"Resolution">>300. Then I change the size by disconnecting the width and height and typing the desired size, in this case 12x16 inches and click "OK". Thats the process I follow and the last step is "Export as" go from there.

I want to know If am following the right method? thank you so much I appreciate you for all your time.

Cheers

[D Fosse]

You don't "pump the DPI to 300". If that involves resampling the image pixels, that is precisely what you don't do. That was my whole point.

The original file is just pixels. Pixels per inch is not a property of the file. Ppi is just a measure of pixel density on paper. Pixels per inch! It doesn't affect the file by itself. You can print the file at any size you want without changing it, and the ppi number is inverse to the print size. The bigger the print, the lower the ppi. The smaller the print, the higher the ppi. Pixels per inch!

You need a minimum pixel density for any print to look crisp and sharp. So that puts a limit to how big any particular file can be printed and still look good. But what that number is, depends on the purpose and process and not the least - the viewing distance. The further away, the lower the required ppi for the same visual result. I just finished a wall-sized banner at 10 ppi. It will look smashing, because it's high up on a wall.

The reason you often hear "300 ppi for print" is that for a standard offset book and magazine print process, this is a theoretical number beyond which no improvement is possible. So anything above 300 ppi is wasted, there is no improvement.

For inkjet 300 ppi has no particular significance, any more than any other number. The main factor is viewing distance.

Ppi is perhaps the most myth-shrouded and misunderstood concept in all of digital image processing. It becomes a lot simpler if you read it literally, word for word: pixels per inch. That's all it means, and that's exactly what it means.

[NB, colourmanagement net]

I agree with D Fosse,

Resampling your images is to be avoided as far as possible.

It may, in some cases, be inevitable to reach the actual size you need but must certainly not be done multiple times 

if you want a 300 PPI*( image, as per the instructions you've received then you will need to set the resolution (in image size - with 'resample' unchecked) and see what physical dimensions your image can attain when PPI is set to 300. You are simply instructing imaging applications to use the pixels in a certain way, (so many for each inch printed) neither creating nor destroying pixels (which is what resampling does).

Maybe it comes out 11 x 16" and you want 12 x16. These 2 are different proportions so the image has to be cropped (or distorted) - then expanded (for which you would have to use resampling) to attain the desired size and proportion. 

Read some articles about image sizing and you'll eventually grasp it. It takes a bit to understand and is hard to explain without a one to one conversation using examples

I hope this helps

thanks
neil barstow, colourmanagement.net :: adobe forum volunteer
[please do not use the reply button on a message within the thread, only use the blue reply button at the top of the page, this maintains the original thread title and chronological order of posts]